JP2013165256A - Laser beam control device and extreme ultraviolet light generation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize laser beam condensation performance.SOLUTION: A laser beam control device includes: a first wavefront regulator constructed to regulate a wavefront of a laser beam outputted from a laser device; a beam transmitter constructed to transmit the laser beam outputted from the first wavefront regulator; a second wavefront regulator constructed to regulate the wavefront of the laser beam outputted from the beam transmitter; a beam monitor constructed to receive a part of the laser beam outputted from the second wavefront regulator and output a value detected with respect to the received light; and a controller constructed to receive input of the detected value and control the first and second wavefront regulators.

Description

  The present disclosure relates to a laser beam control device and an extreme ultraviolet light generation device.

  In recent years, along with miniaturization of semiconductor processes, miniaturization of transfer patterns in optical lithography of semiconductor processes has been rapidly progressing. In the next generation, fine processing of 70 nm to 45 nm, and further fine processing of 32 nm or less will be required. Therefore, for example, in order to meet the demand for fine processing of 32 nm or less, development of an exposure apparatus combining an apparatus for generating extreme ultraviolet (EUV) light with a wavelength of about 13 nm and a reduced projection reflection optical system is expected. .

  As the EUV light generation apparatus, an LPP (Laser Produced Plasma) type apparatus in which plasma generated by irradiating a target material with a laser beam is used, and a DPP (Discharge Produced Plasma) in which plasma generated by discharge is used. Three types of devices have been proposed: a device of the type and an SR (Synchrotron Radiation) type device using synchrotron radiation.

US Patent Application Publication No. 2010/0127191

Overview

  A laser beam control device according to an aspect of the present disclosure includes a first wavefront tuner configured to adjust a wavefront of a laser beam output from the laser device, and an output from the first wavefront tuner. A beam transmitter configured to transmit a laser beam, a second wavefront adjuster configured to adjust a wavefront of the laser beam output from the beam transmitter, and an output from the second wavefront adjuster A beam monitor configured to receive a portion of the received laser beam and configured to output a detection value of the received light; and first and second wavefront modulators for inputting the detection value And a controller configured to control.

  An extreme ultraviolet light generation device according to another aspect of the present disclosure includes a first wavefront adjuster configured to adjust a wavefront of a laser beam output from a laser device, and a first wavefront adjuster. A beam transmitter configured to transmit the output laser beam; a second wavefront adjuster configured to adjust a wavefront of the laser beam output from the beam transmitter; and a second wavefront adjustment A beam monitor configured to receive a part of the laser beam output from the detector, and configured to output a detection value of the received light; A laser beam control device comprising a controller configured to control the wavefront adjuster, a chamber provided with an entrance at a position for introducing a laser beam output from the laser beam control device, Provided Yanba may comprise a target supply unit for supplying a target material to a predetermined region of the chamber, a laser beam focusing optics for focusing the laser beam in the predetermined region.

Several embodiments of the present disclosure are described below by way of example only and with reference to the accompanying drawings.
FIG. 1 schematically shows the configuration of an exemplary LPP type EUV light generation system. FIG. 2 is a partial cross-sectional view of the EUV light generation system according to the first embodiment. FIG. 3A is a diagram for explaining the function of the wavefront adjuster. FIG. 3B is a diagram for explaining the function of the wavefront adjuster. FIG. 4A is a diagram for explaining an operation principle of wavefront adjustment by the first and second wavefront adjusters. FIG. 4B is a diagram for explaining an operation principle of wavefront adjustment by the first and second wavefront adjusters. FIG. 4C is a diagram for explaining an operation principle of wavefront adjustment by the first and second wavefront adjusters. FIG. 5 is a flowchart showing the operation of the controller in the first embodiment. FIG. 6A is a flowchart showing a process for controlling the first wavefront adjuster shown in FIG. 5. FIG. 6B is a flowchart showing details of a process for controlling the first wavefront adjuster shown in FIG. 6A. FIG. 7A is a flowchart showing a process for controlling the second wavefront adjuster shown in FIG. FIG. 7B is a flowchart showing details of a process for controlling the second wavefront tuner shown in FIG. 7A. FIG. 8A schematically shows a first example of a beam monitor in the EUV light generation system according to the first embodiment. FIG. 8B is a diagram for explaining the detection principle when the first example of the beam monitor is applied. FIG. 9 schematically shows a second example of the beam monitor in the EUV light generation system according to the first embodiment. FIG. 10A is a flowchart illustrating a process of controlling the second wavefront adjuster in the case of applying the second example of the beam monitor. FIG. 10B is a flowchart showing details of a process for controlling the second wavefront tuner shown in FIG. 10A. FIG. 10C is a flowchart showing details of a process for controlling the second wavefront tuner shown in FIG. 10A. FIG. 11A schematically shows a third example of the beam monitor in the EUV light generation system according to the first embodiment. FIG. 11B is a diagram for explaining the detection principle when the third example of the beam monitor is applied. FIG. 12 schematically shows a first example of a wavefront adjuster in the EUV light generation system according to the first embodiment. FIG. 13 schematically illustrates a second example of the wavefront adjuster in the EUV light generation system according to the first embodiment. FIG. 14A schematically shows a third example of the wavefront adjuster in the EUV light generation system according to the first embodiment. FIG. 14B schematically shows a third example of the wavefront adjuster in the EUV light generation system according to the first embodiment. FIG. 15 schematically shows a fourth example of the wavefront adjuster in the EUV light generation system according to the first embodiment. FIG. 16A schematically shows a fifth example of the wavefront adjuster in the EUV light generation system according to the first embodiment. FIG. 16B schematically shows a fifth example of the wavefront tuner in the EUV light generation system according to the first embodiment. FIG. 16C schematically shows a fifth example of the wavefront adjuster in the EUV light generation system according to the first embodiment. FIG. 17A schematically shows a sixth example of the wavefront adjuster in the EUV light generation system according to the first embodiment. FIG. 17B schematically shows a sixth example of the wavefront adjuster in the EUV light generation system according to the first embodiment. FIG. 17C schematically illustrates a sixth example of the wavefront adjuster in the EUV light generation system according to the first embodiment. FIG. 18 is a partial cross-sectional view showing the configuration of the VRWM in the fifth and sixth examples of the wavefront tuner. FIG. 19 schematically illustrates a seventh example of the wavefront tuner in the EUV light generation system according to the first embodiment. FIG. 20A is a plan view showing a configuration of a deformable mirror in the seventh example of the wavefront tuner. 20B is a partial cross-sectional view of the deformable mirror shown in FIG. 20A. FIG. 21 is a partial cross-sectional view of an EUV light generation system according to the second embodiment. FIG. 22A schematically shows a first example of a beam monitor in the EUV light generation system according to the second embodiment. FIG. 22B schematically shows a first example of a beam monitor in the EUV light generation system according to the second embodiment. FIG. 23 schematically illustrates a second example of the beam monitor in the EUV light generation system according to the second embodiment. FIG. 24 schematically shows a third example of the beam monitor in the EUV light generation system according to the second embodiment. FIG. 25 schematically shows a part of a modification of the second embodiment. FIG. 26 is a partial cross-sectional view of an EUV light generation system according to the third embodiment. FIG. 27 is a flowchart showing the operation of the controller in the third embodiment. FIG. 28 is a partial cross-sectional view of an EUV light generation system according to the fourth embodiment. FIG. 29 is a partial cross-sectional view of an EUV light generation system according to the fifth embodiment. FIG. 30 is a partial cross-sectional view of an EUV light generation system according to the sixth embodiment. FIG. 31 is a block diagram showing a schematic configuration of each controller.

Embodiment

<Contents>
1. Outline 2. 2. Overall description of extreme ultraviolet light generation system 2.1 Configuration 2.2 Operation EUV light generation system including a wavefront tuner (first embodiment)
3.1 Configuration 3.2 Principle 3.3 Operation 3.3.1 Main Flow 3.3.2 Control of First Wavefront Tuner (Details of S100)
3.3.3 Control of second wavefront adjuster (details of S200)
3.4 Examples of beam monitors 3.4.1 Detection of beam width at two different positions 3.4.2 Detection of beam width and spot width 3.4.3 Use of Shack-Hartmann wavefront sensor 3.5 Wavefront adjuster 3.5.1 Combination of convex mirror and concave mirror 3.5.2 Combination of concave mirror and convex mirror 3.5.3 Combination of two off-axis parabolic concave mirrors 3.5.4 Combination of off-axis paraboloid convex mirror and off-axis paraboloid concave mirror 3.55.5 Use of VRWM 3.5.6 Use of deformable mirror EUV light generation system including a guide laser (second embodiment)
4.1 Configuration 4.2 Examples of beam monitors 4.2.1 Beam width detection at two different locations 4.2.2 Beam width and spot width detection 4.2.3 Use of Shack-Hartmann wavefront sensors 3. Operation 4.4 Arrangement of laser amplifier 5. EUV light generation system that matches the wavefront of the guide laser beam with the wavefront of the laser beam (third embodiment)
5.1 Configuration 5.2 Operation 6. EUV light generation system that matches the wavefront of the laser beam with the wavefront of the guide laser beam (fourth embodiment)
7). EUV light generation system for adjusting the wavefront of a laser beam and the wavefront of a guide laser beam (fifth embodiment)
8). EUV light generation system using a pre-pulse laser (sixth embodiment)
9. Controller configuration

  Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Embodiment described below shows some examples of this indication, and does not limit the contents of this indication. In addition, all the configurations and operations described in the embodiments are not necessarily essential as the configurations and operations of the present disclosure. In addition, the same referential mark is attached | subjected to the same component and the overlapping description is abbreviate | omitted.

1. Outline In the LPP type EUV light generation apparatus, the target material may be converted into plasma by condensing and irradiating the laser beam output from the laser device onto the target material in the chamber. Light including EUV light may be emitted from the plasma. The emitted EUV light may be collected by an EUV collector mirror disposed in the chamber and output to an external apparatus such as an exposure apparatus.

  A beam transmitter including a mirror or the like disposed in a laser beam path from the laser device to the chamber may be heated and deformed by the energy of the laser beam. As a result, the wavefront of the laser beam may be deformed. In that case, the condensing diameter and condensing position of the laser beam irradiated to the target material in the chamber may fluctuate, and the output of EUV light may become unstable.

  According to one aspect of the present disclosure, a wavefront adjuster is disposed at a front stage and a rear stage of a beam transmitter, a laser beam output from the latter wavefront conditioner is detected, and these wavefront adjusters are controlled. Also good.

2. 2. General Description of Extreme Ultraviolet Light Generation System 2.1 Configuration FIG. 1 schematically shows a configuration of an exemplary LPP type EUV light generation system. The EUV light generation apparatus 1 may be used together with at least one laser apparatus 3. In the present application, a system including the EUV light generation apparatus 1 and the laser apparatus 3 is referred to as an EUV light generation system 11. As shown in FIG. 1 and described in detail below, the EUV light generation apparatus 1 may include a chamber 2 and a target supply device 26. The chamber 2 may be sealable. The target supply device 26 may be attached, for example, so as to penetrate the wall of the chamber 2. The material of the target substance supplied from the target supply device 26 may include, but is not limited to, tin, terbium, gadolinium, lithium, xenon, or a combination of any two or more thereof.

  The wall of the chamber 2 may be provided with at least one through hole. The through hole may be provided with a window 21, and the laser beam 32 may pass through the window 21. In the chamber 2, for example, an EUV collector mirror 23 having a spheroidal reflecting surface may be disposed. The EUV collector mirror 23 may have first and second focal points. For example, a multilayer reflective film in which molybdenum and silicon are alternately laminated may be formed on the surface of the EUV collector mirror 23. For example, the EUV collector mirror 23 is preferably arranged such that its first focal point is located in the plasma generation region 25 and its second focal point is located in the intermediate focal point (IF) 292. . A through hole 24 for allowing the laser beam 33 to pass therethrough may be provided at the center of the EUV collector mirror 23.

  The EUV light generation apparatus 1 may further include an EUV light generation control apparatus 5 and a target sensor 4. The target sensor 4 may have an imaging function, and may detect the presence, trajectory, position, speed, and the like of the target.

  Further, the EUV light generation apparatus 1 may include a connection unit 29 that allows the inside of the chamber 2 and the inside of the exposure apparatus 6 to communicate with each other. A wall 291 in which an aperture is formed may be provided inside the connection portion 29. The wall 291 is preferably arranged so that its aperture is located at the second focal point of the EUV collector mirror 23.

  Further, the EUV light generation apparatus 1 may include a laser beam traveling direction control device 34, a laser beam collector mirror 22, a target recovery unit 28 for recovering the target 27, and the like. The laser beam traveling direction control device 34 may include an optical system for defining the traveling direction of the laser beam and an actuator for adjusting the arrangement, posture, and the like of the optical system.

2.2 Operation Referring to FIG. 1, the laser beam 31 output from the laser device 3 passes through the window 21 as the laser beam 32 through the laser beam traveling direction control device 34 and enters the chamber 2. Also good. The laser beam 32 may travel along the at least one laser beam path into the chamber 2, be reflected by the laser beam collecting mirror 22, and be irradiated to the at least one target 27 as the laser beam 33.

  The target supply device 26 may be configured to output the target 27 toward the plasma generation region 25 in the chamber 2. The target 27 may be irradiated with at least one pulse included in the laser beam 33. The target 27 irradiated with the laser beam 33 is turned into plasma, and radiation light 251 can be emitted from the plasma. The EUV light 252 included in the radiation light 251 may be selectively reflected by the EUV collector mirror 23. The EUV light 252 reflected by the EUV collector mirror 23 may be output to the exposure apparatus 6 through the intermediate condensing point 292. A single target 27 may be irradiated with a plurality of pulses included in the laser beam 33.

  The EUV light generation controller 5 may be configured to control the entire EUV light generation system 11. The EUV light generation controller 5 may process image data of the target 27 captured by the target sensor 4. Further, the EUV light generation control device 5 may be configured to control the timing of outputting the target 27, the output direction of the target 27, and the like, for example. Further, the EUV light generation control device 5 may be configured to control, for example, the oscillation timing of the laser device 3, the traveling direction of the laser beam 32, the condensing position of the laser beam 33, and the like. The various controls described above are merely examples, and other controls may be added as necessary.

3. EUV light generation system including a wavefront tuner (first embodiment)
3.1 Configuration FIG. 2 is a partial cross-sectional view of the EUV light generation system according to the first embodiment. In the first embodiment, the chamber 2 may be disposed on the clean room floor, and the laser device 3 may be disposed on the subfab floor. The subfab floor may be located below the clean room floor. The laser beam traveling direction control device 34 for controlling the traveling direction of the laser beam supplied into the chamber 2 from the laser device 3 may be disposed across the clean room floor and the subfab floor. The laser device 3 may be fixed inside the housing 310 by a fixing device (not shown). The casing 310 may be installed on the floor of the subfab floor by three air suspensions 320. When the number of air suspensions 320 is three, the air suspension 320 on the left side in FIG. Further, in the right air suspension 320 in FIG. 2, the air suspension 320 on the back side of the housing 310 is hidden behind the air suspension 320 on the near side. The reason that the number of air suspensions 320 is three is an example of a known three-point support as a method for supporting an optical device, and it is not intended that the three-point support is essential. The air suspension 320 may be replaced with another vibration reducing device.

  In the subfab floor, the laser beam traveling direction control device 34 may include a first wavefront adjuster 81. The first wavefront adjuster 81 may include a plurality of mirrors or a plurality of lenses. Alternatively, a combination of at least one mirror and at least one lens may be included. The first wavefront adjuster 81 may be disposed in the optical path of the laser beam output from the laser device 3.

  In a region extending between the sub-fab floor and the clean room floor, the laser beam traveling direction control device 34 may include a beam transmitter 50. The beam transmitter 50 includes a hollow optical path tube 500. The optical path tube 500 may be in a vacuum, and dry air or an inert gas may be introduced into the optical path tube 500. When dry air, inert gas, or the like is introduced into the optical path tube 500, the gas may have a low pressure close to vacuum. The beam transmitter 50 may guide the laser beam output from the first wavefront adjuster 81 on the subfab floor to the clean room floor. The beam transmitter 50 may include a plurality of high reflection mirrors 51. The plurality of high reflection mirrors 51 may be respectively supported by the plurality of mirror holders 511.

  In the clean room floor, the chamber 2 may be fixed on the chamber reference member 10. The chamber reference member 10 may be fixed on the floor of the clean room floor by the installation mechanism 9. The installation mechanism 9 may have a structure that is widely known as a three-point support structure for optical instruments. The chamber reference member 10 may include an optical element group that constitutes a part of the laser beam traveling direction control device 34.

  In the clean room floor, the laser beam traveling direction control device 34 may include a second wavefront adjuster 82, a light detection unit 55, a controller 58, and high reflection mirrors 59 and 61. The light detection unit 55 and the high reflection mirrors 59 and 61 may be disposed in the chamber reference member 10.

  The second wavefront tuner 82 may include a plurality of mirrors or a plurality of lenses. Alternatively, a combination of at least one mirror and at least one lens may be included. The second wavefront adjuster 82 may be disposed in the optical path of the laser beam propagated to the clean room floor by the beam transmitter 50.

The high reflection mirror 59 may reflect the laser beam output from the second wavefront adjuster 82 toward the light detection unit 55.
The light detection unit 55 may include a beam splitter 56 and a first beam monitor 57. The beam splitter 56 transmits the laser beam reflected by the high reflection mirror 59 toward the high reflection mirror 61 with a high transmittance, and uses a part of the laser beam reflected by the high reflection mirror 59 as a sample light. It may be reflected toward the beam monitor 57. The first beam monitor 57 may have a light receiving surface on which the sample light is incident. The first beam monitor 57 may be configured to output a detection value for calculating a beam width of the sample light on the light receiving surface and a parameter relating to the wavefront to the controller 58. Examples of parameters relating to the wavefront include beam divergence and the like as described later.

  The controller 58 may calculate the beam width of the sample light and the parameter relating to the wavefront based on the detection value output from the first beam monitor 57. The controller 58 uses the above parameter values so that the sample light of the laser beam having a beam width and wavefront within a predetermined range is incident on the light receiving surface of the first beam monitor 57. The wavefront adjusters 81 and 82 may be feedback controlled. A specific example of the control will be described later with reference to FIGS. 3A to 11B.

  The high reflection mirror 61 may reflect the laser beam transmitted through the beam splitter 56 toward the inside of the mirror storage container 60. The mirror container 60 may be provided with a window 66, and the laser beam reflected by the high reflection mirror 61 may pass through the window 66 with high transmittance. The laser beam that has passed through the window 66 is reflected by the flat mirror 62 with a high reflectivity, reflected by the laser light collecting mirror 220 with a high reflectivity, and condensed on the target supplied to the plasma generation region 25. Good. The target is turned into a plasma by being irradiated with a laser beam, and radiation light including EUV light can be emitted from the plasma.

3.2 Principle FIGS. 3A and 3B are diagrams for explaining the function of the wavefront adjuster. The first and second wavefront adjusters 81 and 82 may be optical elements that adjust the wavefront of the laser beam. In FIG. 3A, the first or second wavefront tuner 81 or 82 changes the laser beam having a planar wavefront (plane wave) into a laser beam having a wavefront whose front in the traveling direction is concave. ing. In FIG. 3B, the first or second wavefront tuner 81 or 82 changes a laser beam having a planar wavefront (plane wave) into a laser beam having a wavefront whose front in the traveling direction is a convex surface. ing.

  That is, the first and second wavefront adjusters 81 and 82 may be optical elements that can change the wavefront of the laser beam as shown in FIG. 3A or as shown in FIG. 3B. Good. Further, the first and second wavefront adjusters 81 and 82 may be able to change a wavefront having an arbitrary curvature in a predetermined range to a wavefront having another arbitrary curvature in the predetermined range.

When the wavefront adjuster has a focal length F, the focal power P of the wavefront adjuster can be expressed by the following equation.
P = 1 / F
If F has a positive value, a plane wave can be converted into a laser beam with a wavefront that is focused at a position where the forward distance from the principal point of the wavefront tuner is F ( (See FIG. 3A).
When F has a negative value, the plane wave is converted into a laser beam having a wavefront equivalent to the wavefront of the light generated from the point light source at a position where the distance from the principal point of the wavefront adjuster to the rear is F. (See FIG. 3B).

  4A to 4C are diagrams for explaining the principle of operation of wavefront adjustment by the first and second wavefront adjusters 81 and 82. FIG. The laser beam output from the laser device 3 may enter the chamber 2 through the beam transmitter 50. The length of the optical path from the input end to the output end of the beam transmitter 50 may reach several tens of meters, and the beam transmitter 50 may include a plurality of high reflection mirrors 51.

  When these highly reflective mirrors 51 are heated and deformed by the energy of the laser beam, wavefront distortion may be accumulated in the optical path from the input end to the output end of the beam transmitter 50. For example, even when the laser beam has an optical path and a wavefront indicated by a broken line in FIG. 4A at a low heat load, the laser beam may change to have an optical path and a wavefront indicated by a solid line at FIG. 4A at a high heat load. Thus, when the wavefront changes, the beam width can also change with the progress of the laser beam.

  Therefore, as shown in FIG. 4B, the controller 58 controls the first wavefront adjuster 81 on the basis of the detected value of the beam width on the light receiving surface of the first beam monitor 57, thereby the first beam monitor. The beam width at the light receiving surface 57 may be adjusted to a desired value.

  Further, as shown in FIG. 4C, the controller 58 controls the second wavefront adjuster 82 based on the detected value of the parameter relating to the wavefront on the light receiving surface of the first beam monitor 57, thereby controlling the first beam. The parameter relating to the wavefront on the light receiving surface of the monitor 57 may be adjusted to a desired value.

  In this way, the beam width on the light receiving surface of the first beam monitor 57 and the parameter relating to the wavefront may be adjusted to desired values. According to this, not only the wavefront distortion generated in the beam transmitter 50 but also the wavefront distortion generated in the optical path upstream of the beam transmitter 50 can be adjusted. Note that a second beam monitor (not shown) for detecting the beam width may be disposed in the optical path between the beam transmitter 50 and the second wavefront adjuster 82. That is, the parameter relating to the wavefront may be calculated based on the detection value of the first beam monitor 57, and the beam width may be calculated based on the detection value of the second beam monitor.

3.3 Operation 3.3.1 Main Flow FIG. 5 is a flowchart showing the operation of the controller in the first embodiment. The controller 58 sets the first and second wavefront adjusters 81 and 82 as follows so that the sample light of the laser beam having a desired beam width and wavefront is incident on the light receiving surface of the first beam monitor 57. You may control.

  First, the controller 58 may calculate the beam width of the laser beam based on the detection value of the first beam monitor 57, and may control the first wavefront adjuster 81 based on the calculation result (S100). Next, the controller 58 may calculate a parameter related to the wavefront of the laser beam based on the detection value of the first beam monitor 57, and may control the second wavefront adjuster 82 based on the calculation result (S200). ).

  Thereafter, the controller 58 may determine whether or not to stop the control according to this flowchart by receiving a signal from the EUV light generation controller 5 (S300). When a signal indicating control stop is received from the EUV light generation controller 5 (S300: YES), control may be stopped. When the signal indicating the control stop is not received (S300: NO), the first wavefront adjuster 81 may be controlled by returning to the above-described S100.

3.3.2 Control of first wavefront adjuster (details of S100)
FIG. 6A is a flowchart showing a process for controlling the first wavefront adjuster shown in FIG. 5. The process shown in FIG. 6A may be performed by the controller 58 as a subroutine of S100 shown in FIG.

  First, the controller 58 may receive a signal output from the EUV light generation controller 5 and determine whether a laser beam is output from the laser device 3 (S110). When the laser beam is not output (S110: NO), it may wait until the laser beam is output. When the laser beam is output (S110: YES), the process may be advanced to S120.

In S120, the controller 58 may calculate the beam width D of the laser beam based on the detection value output from the first beam monitor 57. Next, the controller 58 may calculate a difference ΔD from the beam width Dt of the target laser beam by the following formula (S130).
ΔD = D−Dt

  Next, the controller 58 may determine whether or not the absolute value of ΔD is equal to or less than a desired threshold value ΔDr (S140). If the absolute value of ΔD is not less than or equal to the threshold (S140: NO), the process may proceed to S150, and the first wavefront adjuster 81 may be controlled so that the above ΔD approaches 0. When the absolute value of ΔD is equal to or less than the threshold value (S140: YES), the processing according to this flowchart may be terminated.

  FIG. 6B is a flowchart showing details of a process for controlling the first wavefront adjuster shown in FIG. 6A. The process shown in FIG. 6B may be performed by the controller 58 as a subroutine of S150 shown in FIG. 6A.

  First, the controller 58 may compare the above ΔD with 0 (S151). In S151, when the above-described ΔD is equal to 0 (ΔD = 0), the process may be advanced to S152. In S152, the current value P # 1 of the focal power of the first wavefront adjuster 81 may be set as the target focal power P1.

  In S151, when the above ΔD is smaller than 0 (the beam width D is smaller than the target value) (ΔD <0), the process may be advanced to S153. In S153, a value obtained by subtracting a predetermined constant ΔP # 1 from the current value P # 1 of the focal power of the first wavefront adjuster 81 may be set as the target focal power P1. A specific method of focal power control will be described later with reference to FIGS. 3A to 11B.

  In S151, when the above ΔD is larger than 0 (the beam width D is larger than the target value) (ΔD> 0), the process may be advanced to S154. In S154, a value obtained by adding a predetermined constant ΔP # 1 to the current value P # 1 of the focal power of the first wavefront adjuster 81 may be set as the target focal power P1. The predetermined constant ΔP # 1 may be a positive value.

  Next, the controller 58 may output a control signal so that the focal power of the first wavefront adjuster 81 approaches P1 (S155), and the processing according to this flowchart may be terminated.

3.3.3 Control of second wavefront adjuster (details of S200)
FIG. 7A is a flowchart showing a process for controlling the second wavefront adjuster shown in FIG. The process shown in FIG. 7A may be performed by the controller 58 as a subroutine of S200 shown in FIG.

  First, the controller 58 may receive a signal output from the EUV light generation controller 5 and determine whether or not a laser beam is output from the laser device 3 (S210). If the laser beam is not output (S210: NO), the process may wait until the laser beam is output. When the laser beam is output (S210: YES), the process may be advanced to S220.

In S220, the controller 58 may calculate a parameter W related to the wavefront of the laser beam based on the detection value output from the first beam monitor 57. Next, the controller 58 may calculate a difference ΔW from the parameter Wt related to the wavefront of the target laser beam by the following equation (S230).
ΔW = W-Wt

  Next, the controller 58 may determine whether or not the absolute value of ΔW is equal to or less than a desired threshold value ΔWr (S240). If the absolute value of ΔW is not less than or equal to the threshold (S240: NO), the process may proceed to S250, and the second wavefront adjuster 82 may be controlled so that the above ΔW approaches zero. When the absolute value of ΔW is equal to or less than the threshold value (S240: YES), the process according to this flowchart may be terminated.

  FIG. 7B is a flowchart showing details of a process for controlling the second wavefront tuner shown in FIG. 7A. The process shown in FIG. 7B may be performed by the controller 58 as a subroutine of S250 shown in FIG. 7A.

  First, the controller 58 may compare ΔW with 0 described above (S251). In S251, when the above-described ΔW is equal to 0 (ΔW = 0), the process may be advanced to S252. In S252, the current value P # 2 of the focal power of the second wavefront adjuster 82 may be set as the target focal power P2.

  In S251, when the above-described ΔW is smaller than 0 (ΔW <0), the process may be advanced to S253. In S253, a value obtained by subtracting a predetermined constant ΔP # 2 from the current value P # 2 of the focal power of the second wavefront adjuster 82 may be set as the target focal power P2.

  In S251, when the above-described ΔW is larger than 0 (ΔW> 0), the process may be advanced to S254. In S254, a value obtained by adding a predetermined constant ΔP # 2 to the current value P # 2 of the focal power of the second wavefront adjuster 82 may be set as the target focal power P2. The predetermined constant ΔP # 2 may be a positive value. A specific method of focal power control will be described later with reference to FIGS. 3A to 11B.

  Next, the controller 58 may output a control signal so that the focal power of the second wavefront adjuster 82 approaches P2 (S255), and the processing according to this flowchart may be terminated.

3.4 Beam Monitor Example 3.4.1 Detection of Beam Width at Two Different Positions FIG. 8A schematically shows a first example of a beam monitor in the EUV light generation system according to the first embodiment. FIG. 8B is a diagram for explaining the detection principle when the first example of the beam monitor is applied. In the first example, the sample light may be branched by the beam splitter 73, and the light beam transmitted through the beam splitter 73 and the reflected light may have different optical path lengths to detect the respective beam profiles. The beam profile may be, for example, a light intensity distribution in a laser beam cross section. Thereby, the beam profiles at two different positions in the traveling direction of the sample light may be detected. The sample light may be a laser beam that is branched from the laser light path from the laser device 3 to the chamber 2 and is incident on the first beam monitor 57.

  As shown in FIG. 8A, the first beam monitor 57 may include a beam splitter 73, a high reflection mirror 77, transfer optical systems 75 and 79, and beam profilers 570 and 590. The beam profiler may be a line sensor or a CCD camera, for example.

  The beam splitter 73 may transmit part of the sample light toward the transfer optical system 75 and reflect the other part toward the high reflection mirror 77. The high reflection mirror 77 may reflect the light reflected by the beam splitter 73 toward the transfer optical system 79 with a high reflectance.

  The transfer optical system 75 may transfer the beam profile at an arbitrary position A1 between the beam splitter 56 (see FIG. 2) and the beam splitter 73 on the optical path of the sample light to the light receiving surface of the beam profiler 570. The transfer optical system 79 may transfer the beam profile at the position A2 on the optical path of the sample light to the light receiving surface of the beam profiler 590. The distance along the optical path of the sample light between the position A1 and the light receiving surface of the beam profiler 570 may be equal to the distance along the optical path of the sample light between the position A2 and the light receiving surface of the beam profiler 590. The beam profilers 570 and 590 may output data of the beam profile (for example, light intensity distribution) transferred to the light receiving surface to the controller 58.

Based on the output data from the beam profiler 570, the controller 58 determines the beam width Da1 of the laser beam at the position A1 (for example, the width of the portion having an intensity of 1 / e ² or more with respect to the peak intensity in the light intensity distribution). May be calculated.

Further, the controller 58 may calculate a parameter related to the wavefront of the laser beam based on output data from the beam profilers 570 and 590. For example, based on the output from the beam profiler 590, the beam width Da2 of the laser beam at the position A2 (for example, the width of the portion having an intensity of 1 / e ² or more with respect to the peak intensity in the light intensity distribution) is calculated. May be. Then, the controller 58 may calculate a parameter relating to the wavefront of the laser beam from the difference between the beam widths Da1 and Da2 of the laser beam. As a parameter relating to the wavefront, the beam divergence θ may be calculated by the following equation.
θ = tan ⁻¹ {(Da2−Da1) / 2L}
Here, L may be a distance between the position A1 and the position A2 along the optical path of the sample light.

  Based on the above calculation results, the controller 58 may control the first and second wavefront adjusters 81 and 82. The controller 58 may operate in the same manner as the operations shown in the flowcharts of FIGS. 5, 6A, 6B, 7A, and 7B. Note that the beam width D in FIG. 6A may be read as the beam width Da1. Further, the parameter W relating to the wavefront and the parameter Wt relating to the wavefront of the target laser beam in FIG. 7A may be read as the beam divergence θ and the target beam divergence θt, respectively.

3.4.2 Detection of Beam Width and Spot Width FIG. 9 schematically shows a second example of a beam monitor in the EUV light generation system according to the first embodiment. In the second example, the sample light may be branched by the beam splitter 73 in order to detect the beam profile of the beam cross section of the sample light and the spot width of the collected sample light.

As shown in FIG. 9, the beam monitor may include a beam splitter 73, a condensing optical system 74, a transfer optical system 75, and beam profilers 540 and 570.
The beam splitter 73 may transmit a part of the sample light toward the transfer optical system 75 and reflect the other part toward the condensing optical system 74.

  The transfer optical system 75 may transfer the beam profile at the position A1 on the optical path of the sample light to the light receiving surface of the beam profiler 570. The condensing optical system 74 may condense the light reflected by the beam splitter 73 onto the light receiving surface of the beam profiler 540 disposed at a position away from the condensing optical system 74 by a predetermined distance X.

  The predetermined distance X may be a distance at which a laser beam having a required wavefront is focused by the condensing optical system 74. The requested wavefront may be a wavefront that is set so that a predetermined focusing performance can be realized in the plasma generation region 25 when the laser beam is focused by the laser beam focusing mirror 220. When the requested wavefront is a plane wave, the predetermined distance X may be the focal length of the condensing optical system 74. When the requested wavefront is a wavefront whose front in the traveling direction is a convex surface, the predetermined distance X may be longer than the focal length of the condensing optical system 74. When the requested wavefront is a wavefront whose front in the traveling direction is a concave surface, the predetermined distance X may be shorter than the focal length of the condensing optical system 74. The beam profilers 540 and 570 may output data of beam profiles (for example, light intensity distribution) imaged and transferred to the light receiving surface to the controller 58, respectively.

Based on the output from the beam profiler 570, the controller 58 determines the beam width D of the laser beam at the position A1 (for example, the width of the portion having an intensity of 1 / e ² or more with respect to the peak intensity of the light intensity distribution). It may be calculated. Further, the controller 58 may calculate a parameter related to the wavefront of the laser beam based on the output from the beam profiler 540. As a parameter relating to the wavefront, the spot width Sd of the collected sample light (for example, the width of a portion having an intensity of 1 / e ² or more with respect to the peak intensity of the light intensity distribution) may be calculated.

  Based on the above calculation results, the controller 58 may control the first and second wavefront adjusters 81 and 82. The controller 58 may operate in the same manner as shown in the flowcharts of FIGS. 5, 6A, and 6B. In addition, about the process which controls a 2nd wavefront regulator, you may perform the following operation | movement instead of the operation | movement shown to the flowchart of FIG. 7A and FIG. 7B.

  FIG. 10A is a flowchart illustrating a process of controlling the second wavefront adjuster in the case of applying the second example of the beam monitor. The process shown in FIG. 10A may be performed by the controller 58 as a subroutine of S200 shown in FIG.

  First, the controller 58 may receive a signal output from the EUV light generation controller 5 and determine whether or not a laser beam is output from the laser device 3 (S260). When the laser beam is not output (S260: NO), it may wait until the laser beam is output. When the laser beam is output (S260: YES), the process may be advanced to S270.

  In S270, the controller 58 may calculate the spot width Sd of the focused laser beam based on the output from the beam profiler 540. Next, the controller 58 may control the second wavefront adjuster 82 so that the spot width Sd becomes small (S280). Next, the controller 58 may determine whether or not the spot width Sd is the minimum value (S290). Specific methods for these determinations will be described later. When the spot width Sd is not the minimum value, the process may return to the above-described S260 and determine whether the output of the laser beam has been started. When the spot width Sd is the minimum value, the processing according to this flowchart may be terminated.

  10B and 10C are flowcharts showing details of processing for controlling the second wavefront adjuster shown in FIG. 10A. The process shown in FIG. 10B may be performed by the controller 58 as a subroutine of S280 shown in FIG. 10A. The process illustrated in FIG. 10C may be performed by the controller 58 as a subroutine of S290 illustrated in FIG. 10A.

  As shown in FIG. 10B, the controller 58 may determine whether there is data of the spot width value Spd measured immediately before the current spot width Sd is measured (S280a). When the data of the spot width value Spd measured immediately before does not exist (Spd = NULL) (S280a: NO), the controller 58 sets the current spot width Sd as the value Spd (S280b), and the process is S286. You may proceed to. Alternatively, the controller 58 may advance the process from S280b to S286 instead of S285. On the other hand, if there is data of the spot width value Spd measured immediately before (S280a: YES), the controller 58 may advance the process to S281.

  In S281, the current spot width Sd may be compared with the spot width value Spd measured immediately before that. When the current spot width Sd is smaller than the spot width value Spd measured immediately before (Sd <Spd), the process may be advanced to S282. In S282, the flag value Flgp set immediately before setting the flag Flg (described later) may be determined. The value Flgp may be set to a first value (for example, +1) when the focal power of the second wavefront adjuster 82 has been increased immediately before. If the focal power of the second wavefront adjuster 82 has been lowered immediately before, the second value (for example, −1) may be set as the value Flgp.

  In S282, when the value Flgp is the first value (+1), the focal power of the second wavefront tuner 82 may be further increased. That is, in S286, a value obtained by adding a predetermined constant ΔP # 2 to the current value P # 2 of the focal power of the second wavefront adjuster 82 may be set as the target focal power P2. The predetermined constant ΔP # 2 may be a positive value.

  In S282, when the value Flgp is the second value (−1), the focal power of the second wavefront adjuster 82 may be further decreased. That is, in S285, a value obtained by subtracting the predetermined constant ΔP # 2 from the current value P # 2 of the focal power of the second wavefront adjuster 82 may be set as the target focal power P2.

  In S281, when the current spot width Sd is larger than the spot width value Spd measured immediately before (Sd> Spd), the process may proceed to S283. In S283, the value of the flag Flg may be determined.

  In S283, when the value Flgp is the first value (+1), the focal width of the second wavefront adjuster 82 is increased immediately before that, so that the second width is increased. The focal power of the wavefront adjuster 82 may be lowered. That is, in S285, a value obtained by subtracting the predetermined constant ΔP # 2 from the current value P # 2 of the focal power of the second wavefront adjuster 82 may be set as the target focal power P2.

  In S283, when the value Flgp is the second value (−1), the focal width of the second wavefront adjuster 82 is lowered immediately before the spot width has increased. The focal power of the wavefront adjuster 82 may be increased. That is, in S286, a value obtained by adding a predetermined constant ΔP # 2 to the current value P # 2 of the focal power of the second wavefront adjuster 82 may be set as the target focal power P2.

  In S286, after raising the target focal power of the second wavefront adjuster 82, the value of the flag Flg may be set to the first value (+1) (S286a), and the process may proceed to S287.

  In S285, after the target focal power of the second wavefront adjuster 82 is lowered, the value of the flag Flg may be set to the second value (−1) (S285a), and the process may proceed to S287.

  In S281, if the current spot width Sd and the spot width value Spd measured immediately before are substantially equal (Sd = Spd), it may be determined that the spot width Sd has reached the minimum value. That is, in S284, the current value P # 2 of the focal power of the second wavefront adjuster 82 may be set as the target focal power P2. Next, the controller 58 may set the flag Flg to a third value (for example, 0) (S284a), and may advance the process to S287.

  In S287, the controller 58 may output a control signal so that the focal power of the second wavefront tuner 82 becomes P2, and the processing shown in FIG. 10B may be terminated.

  As shown in FIG. 10C, the controller 58 determines whether or not the value of the current flag Flg is different from the flag value Flgp set immediately before it, and whether or not the value of the current flag Flg is 0. It may be determined (S291). In S291, when the value of the current flag Flg is equal to the value of the flag Flgp set immediately before it, and the value of the current flag Flg is not 0 (S291: NO), the second wavefront controller 82. It can mean that the focal power is continuously increased or decreased continuously. Therefore, the controller 58 may determine that the spot width Sd has not reached the minimum value (S292), and may advance the process to S294.

  In S291, when the current value of the flag Flg is different from the value of the flag Flgp set immediately before (S291: YES), the focal power of the second wavefront regulator 82 is increased and then decreased this time. Can mean that. Alternatively, it may mean that the focal power of the second wavefront adjuster 82 is lowered and then raised this time. Therefore, the controller 58 may determine that the spot width Sd has reached the minimum value (S293), and may end the process shown in FIG. 10C. Further, if the current value of the flag Flg is 0 (S291: YES), it may mean that the focal power of the second wavefront adjuster 82 is not increased or decreased this time. Therefore, the controller 58 may determine that the spot width Sd has reached the minimum value (S293), and may end the process shown in FIG. 10C.

  In S294, the controller 58 may store the data of the current laser beam spot width Sd as the above-described value Spd. Further, the controller 58 may store the data of the current flag Flg as the above-described value Flgp. And the controller 58 may complete | finish the process shown to FIG. 10C, and may return a process to above-mentioned S260. Note that the value Spd stored here may be used as the value Spd when the process illustrated in FIG. 10B is executed again. Further, the value Flgp stored here may be used as the value Flgp when the processing shown in FIGS. 10B and 10C is executed again.

3.4.3 Use of Shack-Hartmann Wavefront Sensor FIG. 11A schematically shows a third example of a beam monitor in the EUV light generation system according to the first embodiment. FIG. 11B is a diagram for explaining the detection principle when the third example of the beam monitor is applied. In the third example, a Shack-Hartmann wavefront sensor may be used to measure the beam width of the sample light and a parameter related to the wavefront (eg, wavefront curvature).

  As shown in FIG. 11A, the Shack-Hartmann wavefront sensor 90 as a beam monitor may include a microlens array 91 and a CCD (charge coupled device) camera 93.

  The microlens array 91 may be an optical element in which a plurality of minute convex lenses or concave lenses are two-dimensionally arranged. The CCD camera 93 may be an element for imaging the interference fringes formed by the microlens array 91.

  The controller 58 may calculate the beam width of the laser beam and the curvature of the wavefront based on the output from the CCD camera 93. The shape of the interference fringes formed by the microlens array 91 (for example, the interval between light intensity peaks in the interference fringes) may depend on the wavelength of the sample light and the curvature of the wavefront. Therefore, if the wavelength of the sample light is known, the curvature of the wavefront of the sample light can be calculated from the shape of the interference fringes.

Further, as shown in FIG. 11B, an approximate curve of the light intensity distribution in the beam cross section of the sample light can be detected by detecting the envelope of the light intensity distribution of the interference fringes formed by the microlens array 91. Therefore, the beam width D of the sample light (for example, the width of the portion having an intensity of 1 / e ² or more with respect to the peak intensity) may be calculated from the envelope.

  Based on the above calculation results, the controller 58 may control the first and second wavefront adjusters 81 and 82. The controller 58 may operate in the same manner as the operations shown in the flowcharts of FIGS. 5, 6A, 6B, 7A, and 7B. The parameter W relating to the wavefront and the parameter Wt relating to the wavefront of the target laser beam in FIG. 7A may be read as the wavefront curvature and the target wavefront curvature, respectively.

3.5 Example of Wavefront Tuner 3.5.1 Combination of Convex Mirror and Concave Mirror FIG. 12 schematically shows a first example of a wavefront tuner in the EUV light generation system according to the first embodiment. . In the first example, the wavefront adjuster 81 or 82 may include a convex mirror 801, a concave mirror 802, and a drive mechanism (not shown). Note that the convex and concave surfaces of the convex mirror 801 and the concave mirror 802 may be spherical, and the laser beam may be a substantially spherical wave. Further, the light intensity distribution of the laser beam may be substantially Gaussian.

  The convex mirror 801 of the wavefront adjuster 81 may be fixed by a mirror holder (not shown) at a position where the laser beam output from the laser device 3 (see FIG. 2) is incident. The convex mirror 801 may reflect the laser beam output from the laser device 3 toward the concave mirror 802. The concave mirror 802 may be supported by the drive mechanism via a mirror holder (not shown) so that the concave mirror 802 can move along the optical path of the laser beam reflected by the convex mirror 801. The concave mirror 802 may reflect the laser beam reflected by the convex mirror 801 toward an optical element disposed between the chamber 2 and the chamber 2 (see FIG. 2). The convex mirror 801 of the wavefront adjuster 82 may be fixed by a mirror holder (not shown) at a position where the laser beam output from the beam transmitter 50 is incident. The function of the convex mirror 801 and the arrangement and function of the concave mirror 802 may be substantially the same as those in the wavefront adjuster 81 described above.

  The drive mechanism may adjust the distance between the convex mirror 801 and the concave mirror 802 by moving the concave mirror 802 in the direction of arrow Y in the optical path of the laser beam reflected by the convex mirror 801. By adjusting the distance between the convex mirror 801 and the concave mirror 802, the wavefront of the laser beam reflected from the concave mirror 802 can be adjusted.

3.5.2 Combination of concave mirror and convex mirror FIG. 13 schematically shows a second example of the wavefront adjuster in the EUV light generation system according to the first embodiment. In the second example, the wavefront adjuster 81 or 82 may include a concave mirror 802, a convex mirror 801, and a drive mechanism (not shown).

  The concave mirror 802 of the wavefront adjuster 81 may be fixed by a mirror holder (not shown) at a position where the laser beam output from the laser device 3 (see FIG. 2) is incident. The concave mirror 802 may reflect the laser beam output from the laser device 3 toward the convex mirror 801. The convex mirror 801 may be supported by the drive mechanism via a mirror holder (not shown) so that the convex mirror 801 can move along the optical path of the laser beam reflected by the concave mirror 802. The convex mirror 801 may reflect the laser beam reflected by the concave mirror 802 toward the optical element disposed between the chamber 2 (see FIG. 2). The concave mirror 802 of the wavefront adjuster 82 may be fixed by a mirror holder (not shown) at a position where the laser beam output from the beam transmitter 50 is incident. The function of the concave mirror 802, the arrangement and function of the convex mirror 801, and the like may be substantially the same as those in the wavefront controller 81 described above.

  The drive mechanism may adjust the distance between the convex mirror 801 and the concave mirror 802 by moving the convex mirror 801 in the direction of arrow Y in the optical path of the laser beam reflected by the concave mirror 802. By adjusting the distance between the convex mirror 801 and the concave mirror 802, the wavefront of the laser beam reflected from the convex mirror 801 can be adjusted.

3.5.3 Combination of two off-axis parabolic concave mirrors FIGS. 14A and 14B schematically show a third example of a wavefront adjuster in the EUV light generation system according to the first embodiment. In the third example, the wavefront adjuster 81 or 82 includes two plane mirrors 811 and 812, two off-axis paraboloid concave mirrors 813 and 814, a mirror fixing plate 815, a drive mechanism (FIG. (Not shown).

  The plane mirror 811 of the wavefront adjuster 81 may be fixed by a mirror holder (not shown) at a position where the laser beam output from the laser device 3 (see FIG. 2) is incident. The plane mirror 811 may reflect the laser beam output from the laser device 3 toward the plane mirror 812.

  The plane mirror 812 may be fixed to the mirror fixing plate 815 and the drive mechanism via a mirror holder (not shown) so that the plane mirror 812 can move along the optical path of the laser beam reflected by the plane mirror 811. The flat mirror 812 may reflect the laser beam reflected by the flat mirror 811 toward the off-axis paraboloid concave mirror 813.

  The off-axis paraboloidal concave mirror 813 may be fixed to the mirror fixing plate 815 and the drive mechanism via a mirror holder (not shown) so that it can move together with the plane mirror 812. The off-axis paraboloid concave mirror 813 focuses the laser beam reflected by the plane mirror 812 on the focal point of the off-axis paraboloid concave mirror 814 and irradiates the off-axis paraboloid concave mirror 814. You may be able to reflect. When the laser beam output from the laser device 3 is a plane wave, the focal position of the off-axis parabolic concave mirror 813 and the focal position of the off-axis parabolic concave mirror 814 may be the same. .

  The off-axis paraboloid concave mirror 814 may be fixed by a mirror holder (not shown) at a position where the laser beam reflected by the off-axis paraboloid concave mirror 813 is incident. The off-axis paraboloid concave mirror 814 may reflect the laser beam reflected by the off-axis paraboloid concave mirror 813 toward an optical element disposed between the chamber 2 (see FIG. 2). .

  The mirror fixing plate 815 may be moved in the arrow Y direction by the drive mechanism so that the distance between the mirror fixing plate 815, the flat mirror 811 and the off-axis paraboloid concave mirror 814 expands and contracts. The wavefront of the laser beam can be adjusted by expanding and contracting the distance between the mirror fixing plate 815, the plane mirror 811 and the off-axis paraboloid concave mirror 814. The configuration and function of the wavefront tuner 82 may be substantially the same as that in the wavefront tuner 81.

3.5.4 Combination of off-axis paraboloid convex mirror and off-axis paraboloid concave mirror FIG. 15 is a schematic diagram of a fourth example of the wavefront adjuster in the EUV light generation system according to the first embodiment. Shown in In the fourth example, the wavefront adjuster 81 or 82 includes an off-axis paraboloid convex mirror 821, an off-axis paraboloid concave mirror 822, two plane mirrors 823 and 824, and a mirror fixing plate 825. And a drive mechanism (not shown).

  The off-axis paraboloid convex mirror 821 of the wavefront adjuster 81 may be fixed by a mirror holder (not shown) at a position where the laser beam output from the laser device 3 (see FIG. 2) is incident. The off-axis paraboloid convex mirror 821 may reflect the laser beam output from the laser device 3 toward the off-axis paraboloid concave mirror 822. The reflected light from the off-axis paraboloid convex mirror 821 may be adjustable so that it can be regarded as light having a wavefront equivalent to the light emitted from the focal point of the off-axis paraboloid concave mirror 822. When the laser beam output from the laser device 3 is a plane wave, the focal position of the off-axis paraboloid convex mirror 821 and the focal position of the off-axis paraboloid concave mirror 822 may be the same. .

  The off-axis paraboloid concave mirror 822 is fixed to the mirror fixing plate 825 via a mirror holder (not shown) so that it can move along the optical path of the laser beam reflected by the off-axis paraboloid convex mirror 821. May be. The off-axis paraboloid concave mirror 822 may reflect the laser beam reflected by the off-axis paraboloid convex mirror 821 toward the plane mirror 823.

  The flat mirror 823 may be fixed to the mirror fixing plate 815 via a mirror holder (not shown) so that it can move together with the off-axis paraboloid concave mirror 822. The plane mirror 823 may reflect the laser beam reflected by the off-axis paraboloid concave mirror 822 toward the plane mirror 824.

  The plane mirror 824 may be fixed to the optical path of the laser beam reflected by the plane mirror 823 by a mirror holder (not shown). The flat mirror 824 may reflect the laser beam reflected by the flat mirror 823 toward an optical element disposed between the flat mirror 824 and the chamber 2 (see FIG. 2).

  The mirror fixing plate 825 may be moved in the arrow Y direction by the drive mechanism so that the distance between the mirror fixing plate 825 and the off-axis paraboloid convex mirror 821 and the plane mirror 824 expands and contracts. The wavefront of the laser beam can be adjusted by expanding and contracting the distance between the mirror fixing plate 825, the off-axis paraboloidal convex mirror 821, and the plane mirror 824. The configuration and function of the wavefront adjuster 82 may be substantially the same as that in the wavefront adjuster 81.

3.5.5 Utilization of VRWM FIGS. 16A to 16C schematically show a fifth example of the wavefront adjuster in the EUV light generation system according to the first embodiment. In the fifth example, the wavefront adjuster 81 or 82 may include a VRWM (Variable Radius Wavefront Mirror) 85.

  The VRWM 85 may be a mirror that can change the curvature of the reflecting surface. A specific configuration example for changing the curvature of the reflecting surface will be described later with reference to FIG. The VRWM 85 may be able to be transformed into a flat mirror as shown in FIG. 16A. The VRWM 85 may be able to be deformed into a concave mirror having a focal point at a position where the distance from the position of the VRWM 85 is + F as shown in FIG. 16B. The VRWM 85 may be able to be transformed into a convex mirror having a focal point at a position where the distance from the position of the VRWM 85 in the direction opposite to the traveling direction of the reflected light is F, as shown in FIG. 16C. Thereby, the VRWM 85 can adjust the wavefront of the laser beam.

  17A to 17C schematically show a sixth example of the wavefront adjuster in the EUV light generation system according to the first embodiment. In the sixth example, the wavefront adjuster 81 or 82 may include a VRWM 85 and a plane mirror 86.

  The VRWM 85 may be a mirror that can change the curvature of the reflecting surface. A specific configuration example for changing the curvature of the reflecting surface will be described later with reference to FIG. The position of the VRWM 85 may be fixed to the optical path of the laser beam output from the laser device 3 (see FIG. 2) by a mirror holder (not shown). The VRWM 85 may reflect the laser beam output from the laser device 3 toward the flat mirror 86.

  The plane mirror 86 may be fixed to the optical path of the laser beam reflected by the VRWM 85 by a mirror holder (not shown). The plane mirror 86 may reflect the laser beam reflected by the VRWM 85 toward an optical element disposed between the flat mirror 86 and the chamber 2 (see FIG. 2).

  In the above configuration, the wavefront of the laser beam can be adjusted by adjusting the curvature of the reflecting surface of the VRWM85.

  FIG. 18 is a partial cross-sectional view showing the configuration of the VRWM in the fifth and sixth examples of the wavefront tuner. The VRWM 85 may include a pressure vessel 851, a reflection plate 852, a supply pipe 853, a discharge pipe 854, and a pressure regulator 855.

  The pressure vessel 851 may be a rigid vessel that contains a liquid such as water. The reflection plate 852 may be an elastic plate fitted into the opening of the pressure vessel 851. One surface of the reflection plate 852 may include a reflection layer that can reflect the laser beam with high reflectivity, and the surface of the reflection layer may be exposed to the outside of the pressure vessel 851.

  One end of each of the supply pipe 853 and the discharge pipe 854 may be connected to the pressure vessel 851. The other ends of the supply pipe 853 and the discharge pipe 854 may be connected to the pressure regulator 855.

  The pressure regulator 855 may increase the pressure in the pressure vessel 851 by supplying a liquid from the supply pipe 853 into the pressure vessel 851 based on a control signal output from the controller 58. The pressure regulator 855 may reduce the pressure in the pressure vessel 851 by discharging the liquid in the pressure vessel 851 from the discharge pipe 854 based on the control signal output from the controller 58.

  The curvature of the reflective layer of the reflective plate 852 may be adjusted by increasing or decreasing the pressure in the pressure vessel 851. Thereby, the curvature of the wavefront of the laser beam reflected by the reflection layer of the reflection plate 852 may be adjusted.

3.5.6 Use of Deformable Mirror FIG. 19 schematically illustrates a seventh example of the wavefront adjuster in the EUV light generation system according to the first embodiment. In the seventh example, the wavefront adjuster 81 or 82 may include a deformable mirror 87.

  The deformable mirror 87 may be a mirror that can change the shape of the reflecting surface. The position of the deformable mirror 87 may be fixed to the optical path of the laser beam output from the laser device 3 (see FIG. 2) by a mirror holder (not shown). The deformable mirror 87 can correct the wavefront with high accuracy by controlling the shape of the reflecting surface even if the laser beam has a wavefront having a shape different from that of the spherical surface.

  The wavefront adjuster 81 or 82 may further include a plane mirror 88. The deformable mirror 87 may reflect the laser beam output from the laser device 3 toward the plane mirror 88.

  The plane mirror 88 may be fixed to the optical path of the laser beam reflected by the deformable mirror 87 by a mirror holder (not shown). The plane mirror 88 may reflect the laser beam reflected by the deformable mirror 87 toward an optical element disposed between the flat mirror 88 and the chamber 2 (see FIG. 2).

  FIG. 20A is a plan view showing a configuration of a deformable mirror in the seventh example of the wavefront tuner. 20B is a partial cross-sectional view of the deformable mirror shown in FIG. 20A. The deformable mirror 87 may include a substrate 871, an insulating layer 872, a plurality of lower electrodes 873, a plurality of piezoelectric members 874, an upper electrode 875, and a reflective layer 876.

  The substrate 871 may be a substrate for integrally forming the deformable mirror 87. The insulating layer 872 may be formed on the upper surface side of the substrate 871. The plurality of lower electrodes 873 may be formed on the upper surface side of the insulating layer 872 at positions separated from each other. The plurality of piezoelectric members 874 may be formed on the upper surface side of the plurality of lower electrodes 873, respectively. The upper electrode 875 may be formed as a common electrode in contact with the upper surface side of the plurality of piezoelectric members 874. The reflective layer 876 may be formed on the upper surface side of the upper electrode 875 so that the laser beam can be reflected with high reflectance on the surface.

In the above configuration, the common potential V ₀ may be applied to the upper electrode 875 and the potentials V _{1 to} V ₇ may be applied to the plurality of lower electrodes 873 by a voltage control circuit (not shown). Accordingly, the surface shape of the reflective layer 876 may be changed by deforming each of the plurality of piezoelectric members 874.

4). EUV light generation system including a guide laser (second embodiment)
4.1 Configuration FIG. 21 is a partial cross-sectional view of an EUV light generation system according to the second embodiment. The EUV light generation system according to the second embodiment includes a laser beam traveling direction adjustment mechanism in order from the laser device 3 side of the beam transmitter 50 on the optical path of the laser beam output from the laser device 3 on the sub-fab floor. 41, a laser beam combiner 44, and a light detector 45 may be included. The guide laser device 40 may be installed so that the guide laser beam output from the guide laser device 40 enters the laser beam combiner 44. Furthermore, a controller 48 may be installed. It should be noted that the controller 48 may be omitted if the controller 58 can share the function of the controller 48. In that case, each component connected to the controller 48 may be connected to the controller 58.

  The guide laser device 40 may be configured to output a guide laser beam different from the laser beam output from the laser device 3. The guide laser device 40 may be a laser device that continuously oscillates (CW oscillation) or a laser device that performs pulse oscillation at a predetermined repetition rate. The average output light energy of the guide laser beam may be lower than the average output light energy of the laser beam output from the laser device 3. Further, the guide laser beam may include light having a wavelength component different from that of the laser beam output from the laser device 3.

  The laser beam traveling direction adjusting mechanism 41 may include high reflection mirrors 42 and 43. The high reflection mirror 42 may be supported by the mirror holder 421, and the position and posture of the high reflection mirror 42 and the mirror holder 421 may be adjusted by the actuator unit 422. Similarly, the high reflection mirror 43 may be supported by the mirror holder 431, and the position and posture of the high reflection mirror 43 and the mirror holder 431 may be adjusted by the actuator unit 432. The traveling direction of the laser beam output from the laser device 3 may be adjusted by adjusting the positions and postures of the high reflection mirrors 42 and 43.

  The laser beam combiner 44 may include a dichroic mirror. The laser beam output from the laser device 3 may be incident on the first surface (the left surface in the drawing) of the laser beam combiner 44. The guide laser beam output from the guide laser device 40 may be incident on the second surface (the right surface in the drawing) of the laser beam combiner 44. The laser beam combiner 44 may transmit the laser beam incident on the first surface and reflect the guide laser beam incident on the second surface. The laser beam combiner 44 is configured so that the traveling direction of the laser beam output from the laser device 3 and the traveling direction of the guide laser beam output from the guide laser device 40 substantially coincide with each other. May be installed at a predetermined installation angle.

  The light detection unit 45 may include a beam sampler 46 and a second beam monitor 47. The beam sampler 46 transmits the laser beam output from the laser device 3 and the guide laser beam output from the guide laser device 40 with high transmittance, and uses each part of the laser beam and the guide laser beam as respective sample light. It may be reflected. The second beam monitor 47 may have a light receiving surface on which sample light is incident. The second beam monitor 47 may be configured to detect the incident position of the sample light on the light receiving surface and output the detection result.

  The controller 48 may receive the control signal output from the EUV light generation controller 5 and operate as follows. Based on the detection result by the second beam monitor 47, the controller 48 shifts the traveling direction of the laser beam transmitted through the laser beam combiner 44 and the traveling direction of the guide laser beam reflected by the laser beam combiner 44. May be detected. This deviation may be a deviation between the traveling direction of the laser beam in the sample light and the traveling direction of the guide laser beam in the sample light. This shift in the traveling direction may be obtained from a shift in the incident position of each laser beam on the second beam monitor 47. The controller 48 may control the laser beam traveling direction adjusting mechanism 41 in order to reduce the deviation between the traveling direction of the laser beam and the traveling direction of the guide laser beam. In the laser beam traveling direction adjusting mechanism 41, an actuator driver (not shown) adjusts the traveling direction of the laser beam output from the laser device 3 by driving the actuator units 422 and 432 in response to a control signal from the controller 48. May be. The controller 48 may have a function of transmitting a control signal to the guide laser device 40 and outputting or stopping the guide laser beam at a desired timing.

  In the second embodiment, the beam transmitter 50 may include high reflection mirrors 52 and 53. The high reflection mirror 52 may be supported by the mirror holder 521, and the position and posture of the high reflection mirror 52 and the mirror holder 521 may be adjusted by the actuator unit 522. Similarly, the high reflection mirror 53 may be supported by the mirror holder 531, and the position and posture of the high reflection mirror 53 and the mirror holder 531 may be adjusted by the actuator unit 532. The traveling directions of the laser beam and the guide laser beam may be adjusted by adjusting the positions and postures of the high reflection mirrors 52 and 53.

  The high reflection mirror 59 may reflect the laser beam and the guide laser beam propagated to the clean room floor by the beam transmitter 50 toward the beam splitter 56. The beam splitter 56 may transmit the laser beam reflected by the high reflection mirror 59 toward the high reflection mirror 61 with high transmittance. The beam splitter 56 may reflect the guide laser beam reflected by the high reflection mirror 59 toward the first beam monitor 57 with high reflectivity as sample guide light. The first beam monitor 57 detects not only the detection values for calculating the parameters relating to the beam width and wavefront of the sample guide light, but also detects the incident position of the sample guide light on the light receiving surface and outputs the detection values. It may be configured.

The controller 58 may control the beam transmitter 50 so that the laser beam is focused on the plasma generation region 25 based on the detected value of the incident position of the sample guide light by the first beam monitor 57. In the beam transmitter 50, an actuator driver (not shown) may adjust the traveling directions of the laser beam and the guide laser beam by driving the actuator units 522 and 532 in response to a control signal from the controller 58.
About another point, it may be the same as that of 1st Embodiment.

  According to the second embodiment, the guide laser beam is detected by the first beam monitor 57, and the controller 58 controls the beam transmitter 50, whereby the traveling direction of the laser beam can be stabilized. Further, the controller 58 can control the beam transmitter 50 even when the laser beam from the laser device 3 is not output. Thereby, even in the initial output of the laser beam output from the laser device 3, the traveling direction of the laser beam can be controlled in a predetermined direction, and the condensing position of the laser beam irradiated to the target material in the chamber is stabilized. obtain.

  Further, according to the second embodiment, even when the laser beam is not output from the laser device 3, the controller 58 performs the first and second operations based on the beam width of the guide laser beam and the parameters relating to the wavefront. The wavefront regulators 81 and 82 can be controlled. As a result, even in the initial output of the laser beam output from the laser device 3, the parameters relating to the beam width and wavefront of the laser beam can be controlled within a predetermined range, and the concentration of the laser beam irradiated to the target material in the chamber can be controlled. The light diameter and the light collection position can be stabilized.

  Up to this point, the description has been given focusing on the guide laser beam received by the first beam monitor 57. However, in the second embodiment, the beam splitter 56 may reflect not only the guide laser beam but also a part of the laser beam toward the first beam monitor 57 as sample light. The first beam monitor 57 may not only receive the guide laser beam, but may further receive the laser beam reflected by the beam splitter 56 and output the detection result. In this case, instead of controlling the laser beam traveling direction adjusting mechanism 41 based on the guide laser beam received by the second beam monitor 47 and the detected value of the laser beam, the laser is generated based on the detected value of the first beam monitor 57. The light traveling direction adjustment mechanism 41 may be controlled. Further, based on the detection value in the first beam monitor 57, the parameters relating to the beam width and wavefront may be calculated not only for the guide laser beam but also for the laser beam.

4.2 Example of Beam Monitor 4.2.1 Detection of Beam Width at Two Different Positions FIGS. 22A and 22B show the second beam monitor 47 or the first in the EUV light generation system according to the second embodiment. A first example of a beam monitor 57 is schematically shown. In the first example, the second beam monitor 47 or the first beam monitor 57 capable of receiving the laser beam and the guide laser beam may include bandpass filters 71 and 72.

  The band pass filters 71 and 72 may be configured to be movable by the drive unit 78. The drive unit 78 may be controlled by the controller 48 or 58. The bandpass filter 71 may be an optical filter that transmits the laser beam output from the laser device 3 with high transmittance and attenuates or blocks light of other wavelengths. The bandpass filter 72 may be an optical filter that transmits the guide laser beam with high transmittance and attenuates or blocks light of other wavelengths.

  As shown in FIG. 22A, when the driving unit 78 moves the bandpass filter 71 on the optical path of the sample light, the laser beam can reach the beam splitter 73. Therefore, the position, traveling direction, beam width, and wavefront curvature of the laser beam can be calculated by the controller 58.

  As shown in FIG. 22B, when the driving unit 78 moves the bandpass filter 72 on the optical path of the sample light, the guide laser beam can reach the beam splitter 73. Accordingly, the controller 58 can calculate the position, traveling direction, beam width, and wavefront curvature of the guide laser beam.

The transfer optical systems 75 and 79 preferably have a function of correcting chromatic aberration with respect to the wavelengths of the laser beam and the guide laser beam. For example, the transfer optical systems 75 and 79 are preferably achromatic lenses or combinations thereof. Furthermore, it is preferable that the transfer optical systems 75 and 79 have a configuration with little chromatic aberration in principle. In the drawing, it is a transmissive optical element, but for example, the transfer optical systems 75 and 79 are preferably reflective optical systems.
Other points may be the same as those described with reference to FIG. 8A.

  According to the first example, since the same beam profilers 570 and 590 are used to detect the laser beam and the guide laser beam, the traveling direction of the laser beam and the traveling direction of the guide laser beam are accurately determined. Deviations can be detected.

4.2.2 Detection of Beam Width and Spot Width FIG. 23 schematically illustrates a second example of the second beam monitor 47 or the first beam monitor 57 in the EUV light generation system according to the second embodiment. Show. In the second example, the second beam monitor 47 or the first beam monitor 57 capable of receiving the laser beam and the guide laser beam may include bandpass filters 71 and 72.

  The band pass filters 71 and 72 may be configured to be movable by the drive unit 78. The drive unit 78 may be controlled by the controller 48 or 58. The bandpass filter 71 may be an optical filter that transmits the laser beam output from the laser device 3 with high transmittance and attenuates or blocks light of other wavelengths. The bandpass filter 72 may be an optical filter that transmits the guide laser beam with high transmittance and attenuates or blocks light of other wavelengths.

  When the driving unit 78 moves the band pass filter 71 on the optical path of the sample light, the laser beam can reach the beam splitter 73. Therefore, the position, traveling direction, beam width, and wavefront curvature of the laser beam can be calculated by the controller 58.

  When the driving unit 78 moves the bandpass filter 72 on the optical path of the sample light, the guide laser beam can reach the beam splitter 73. Accordingly, the controller 58 can calculate the position, traveling direction, beam width, and wavefront curvature of the guide laser beam.

The condensing optical system 74 and the transfer optical system 75 preferably have a function of correcting chromatic aberration with respect to the wavelengths of the laser beam and the guide laser beam. For example, the condensing optical system 74 and the transfer optical system 75 are preferably an achromatic lens or a combination thereof. Furthermore, it is preferable that the condensing optical system 74 and the transfer optical system 75 have a configuration with little chromatic aberration in principle. For example, the condensing optical system 74 and the transfer optical system 75 are preferably reflection optical systems.
Other points may be the same as those described with reference to FIG.

  According to the second example, since the same beam profilers 540 and 570 are used to detect the laser beam and the guide laser beam, the traveling direction of the laser beam and the traveling direction of the guide laser beam are accurately determined. Deviations can be detected.

4.2.3 Use of Shack-Hartmann Wavefront Sensor FIG. 24 schematically shows a third example of the second beam monitor 47 or the first beam monitor 57 in the EUV light generation system according to the second embodiment. . In the third example, the second beam monitor 47 or the first beam monitor 57 that can receive the laser beam and the guide laser beam may include bandpass filters 71 and 72. Further, in the Shack-Hartmann wavefront sensor 90, a screen 92 having a large number of pinholes may be used instead of the microlens array 91.

  The band pass filters 71 and 72 may be configured to be movable by the drive unit 78. The drive unit 78 may be controlled by the controller 48 or 58. The bandpass filter 71 may be an optical filter that transmits the laser beam output from the laser device 3 with high transmittance and attenuates or blocks light of other wavelengths. The bandpass filter 72 may be an optical filter that transmits the guide laser beam with high transmittance and attenuates or blocks light of other wavelengths.

  When the drive unit 78 moves the bandpass filter 71 on the optical path of the sample light, the laser beam can reach the Shack-Hartmann wavefront sensor 90. Therefore, the position, traveling direction, beam width, and wavefront curvature of the laser beam can be calculated by the controller 58.

When the driving unit 78 moves the bandpass filter 72 on the optical path of the sample light, the guide laser beam can reach the Shack-Hartmann wavefront sensor 90. Accordingly, the controller 58 can calculate the position, traveling direction, beam width, and wavefront curvature of the guide laser beam.
Other points may be the same as those described with reference to FIG. 11A.

  According to the third example, since the same Shack-Hartmann wavefront sensor 90 is used to detect the laser beam and the guide laser beam, the traveling direction of the laser beam and the traveling direction of the guide laser beam are accurately determined. Deviations can be detected.

4.3 Operation In the second embodiment having the above-described configuration, the controller 58 causes the first beam monitor 57 to receive the guide laser beam, calculates parameters related to the beam width and the wavefront, and performs the first and second operations. Two wavefront adjusters 81 and 82 may be controlled. The controller 58 may operate in the same manner as the operations shown in the flowcharts of FIGS. 5, 6A, 6B, 7A, and 7B. Note that the laser beam in FIGS. 5, 6A, and 7A may be read as a guide laser beam.

  In the process of controlling the first wavefront adjuster shown in FIG. 6A, the following two steps may be added. Immediately after the start of the subroutine, a step of arranging a band pass filter 72 that transmits the guide laser beam in the optical path of the sample light may be added. Next, a step of transmitting a control signal for causing the guide laser device 40 to output a guide laser beam to the controller 48 may be added. You may perform the process of S110-S150 after these steps.

4.4 Arrangement of Laser Amplifier FIG. 25 schematically shows a modification in which a laser optical amplifier is further added to the second embodiment. In this modification, the laser device 3 may include a master oscillator 300 and amplifiers 301 and 302. Then, amplifiers 303 and 304 for further amplifying the laser beam are provided downstream of the guide laser device 40, the laser beam traveling direction adjusting mechanism 41, and the laser beam coupler 44, which form part of the laser beam traveling direction control device 34. May be arranged. Amplifiers 303 and 304 may be located on the subfab floor.

  The master oscillator 300 may be configured to output seed light of a laser beam for converting the target into plasma. The amplifier 301 may amplify the seed light output from the master oscillator 300, and the amplifier 302 may further amplify the laser beam amplified by the amplifier 301 and output from the amplifier 301.

  The laser beam traveling direction adjusting mechanism 41 may adjust the traveling direction of the laser beam output from the amplifier 302. The guide laser device 40 may be configured to output a guide laser beam. The laser beam combiner 44 substantially matches the traveling direction of the laser beam output from the amplifier 302 and passed through the laser beam traveling direction adjusting mechanism 41 with the traveling direction of the guide laser beam output from the guide laser device 40. You may let them.

  The amplifier 303 may amplify at least the laser beam among the laser beam and the guide laser beam whose traveling directions are matched in the laser beam combiner 44. The amplifier 304 may further amplify at least the laser beam out of the laser beam and the guide laser beam output from the amplifier 303. The laser beam and the guide laser beam output from the amplifier 304 may be partially reflected by the beam sampler 46 and incident on the light detection unit 45 as described with reference to FIG.

  In an EUV light generation system, a target may be irradiated with a laser beam having a high energy in order to output EUV light having a desired energy. When the energy of the laser beam increases, the optical element disposed in the optical path of the laser beam may be deformed by a thermal load, and the traveling direction of the laser beam may change. In particular, when a plurality of amplifiers are used, the energy of the laser beam becomes high at the output portion of the downstream amplifier. For this reason, the change in the wavefront of the laser beam can be greater at the output of the amplifier on the downstream side.

  According to the configuration shown in FIG. 25, by arranging the laser beam combiner 44 between a plurality of amplifiers, the progress of the laser beam at a stage where the change of the wavefront accompanying the deformation of the laser beam combiner 44 due to the thermal load is small. The direction and the traveling direction of the guide laser beam can be matched. Therefore, the difference between the wavefront of the laser beam and the wavefront of the guide laser beam is reduced, and the wavefront of the laser beam can be accurately adjusted based on the wavefront of the guide laser beam.

  Further, as in the third to fifth embodiments to be described later, a wavefront adjuster for reducing the deviation of the wavefronts of the two in the optical path before matching the traveling direction of the laser beam and the traveling direction of the guide laser beam is arranged. In this case, the control amount of the wavefront adjuster can be reduced. If the control amount of the wavefront adjuster can be reduced, the wavefront adjuster can be operated at higher speed and more frequently. As a result, the deviation between the wavefront of the laser beam and the wavefront of the guide laser beam can be stabilized in a small state. The configuration shown in FIG. 25 may also be adopted in third to fifth embodiments described later.

5. EUV light generation system that matches the wavefront of the guide laser beam with the wavefront of the laser beam (third embodiment)
5.1 Configuration FIG. 26 is a partial cross-sectional view of an EUV light generation system according to the third embodiment. The EUV light generation system according to the third embodiment may include a guide laser beam wavefront adjuster 84 between the guide laser device 40 and the laser beam combiner 44 on the sub-fab floor. The configuration of the guide laser beam wavefront tuner 84 may be the same as that of the first or second wavefront tuner 81 or 82.

In the third embodiment, the light detection unit 45 includes bandpass filters 71 and 72 as described with reference to FIGS. 22A, 22B, 23, and 24, and a drive unit that switches these and arranges them in the optical path. 78 may be included. The light detection unit 45 may output detection values for calculating parameters relating to the wavefronts of the laser beam and the guide laser beam. The controller 48 may calculate parameters relating to the wavefronts of the laser beam and the guide laser beam based on the detection value output from the light detection unit 45. The method for calculating the parameter relating to the wavefront may be the same as the method described in the first and second embodiments. The controller 48 may control the guide laser beam wavefront adjuster 84 so that a difference in parameters regarding the wavefronts of the laser beam and the guide laser beam becomes small.
About another point, it may be the same as that of 2nd Embodiment.

  According to the third embodiment, it is possible to reduce the difference between the parameters regarding the wavefronts of the laser beam and the guide laser beam in the light detection unit 45. Therefore, if the first or second wavefront adjuster 81 or 82 is controlled based on the parameter relating to the wavefront of the guide laser beam in the light detection unit 55, the wavefront of the laser beam in the light detection unit 55 can be accurately detected from the initial stage of control. It can be controlled. Thereby, the condensing diameter and condensing position of the laser beam irradiated to the target material in the chamber can be stabilized in a short time after the output of the laser beam from the laser device 3 is started.

5.2 Operation FIG. 27 is a flowchart showing the operation of the controller in the third embodiment. The controller 48 adjusts the guide laser beam wavefront in order to reduce the difference between the parameters relating to the wavefronts of the laser beam output from the laser device 3 and the guide laser beam output from the guide laser device 40 by the following processing. The device 84 may be controlled.

  First, the controller 48 may start the output of the guide laser beam by transmitting a control signal to the guide laser device 40 (S401). Next, the controller 48 may receive a detection signal of the guide laser beam from the second beam monitor 47 (S402). The controller 48 may calculate a parameter Wg related to the wavefront of the guide laser beam based on the detection signal and store it in the storage unit (S403).

  Next, the controller 48 may receive a signal output from the EUV light generation controller 5 and determine whether or not a laser beam is output from the laser device 3 (S404). When the laser beam is not output (S404: NO), the guide laser beam may be detected by returning to S402 described above.

  When the laser beam is output (S404: YES), the controller 48 may receive a laser beam detection signal from the second beam monitor 47 (S405). The controller 48 may calculate a parameter Wd related to the wavefront of the laser beam based on the detection signal and store it in the storage unit (S406).

Next, the controller 48 may calculate the difference ΔWdg between the parameter Wg related to the wavefront of the guide laser beam and the parameter W related to the wavefront of the laser beam by the following equation (S407).
ΔWdg = Wd−Wg

  Next, the controller 48 may determine whether or not the absolute value | ΔWdg | of the parameter difference ΔWdg related to the wavefront is equal to or less than a predetermined threshold value ΔWdg1 (S408).

  In S408, when the absolute value | ΔWdg | is equal to or less than the threshold value ΔWdg1 (S408: YES), the process may be advanced to S409. In S409, the controller 48 may transmit a control signal to the guide laser beam wavefront adjuster 84 in order to make ΔWdg close to zero. Next, the controller 48 may determine whether or not to stop the control according to this flowchart by receiving a signal from the EUV light generation controller 5 (S410). When a signal indicating control stop is received from the EUV light generation controller 5 (S410: YES), the processing may be stopped. When the signal indicating control stop is not received (S410: NO), the process may return to the above-described S402 to detect the guide laser beam.

  If the absolute value | ΔWdg | exceeds the threshold value ΔWdg1 in S408 (S408: NO), the process may proceed to S411. In S411, the controller 48 may transmit a signal indicating an alignment error to the EUV light generation controller 5. Next, similarly to S409, the controller 48 may transmit a control signal to the guide laser beam wavefront adjuster 84 in order to make ΔWdg close to 0 (S412). Then, it may return to above-mentioned S402 and may detect a guide laser beam. The EUV light generation control device 5 that has received the signal indicating the alignment abnormality may perform various processes such as stopping the target supply from the target supply device 26.

6). EUV light generation system that matches the wavefront of the laser beam with the wavefront of the guide laser beam (fourth embodiment)
FIG. 28 is a partial cross-sectional view of an EUV light generation system according to the fourth embodiment. The EUV light generation system according to the fourth embodiment may include a third wavefront adjuster 83 in the optical path of the output laser light of the laser device 3 on the sub-fab floor. The configuration of the third wavefront adjuster 83 may be the same as the configuration of the first or second wavefront adjuster 81 or 82.

In the fourth embodiment, the light detection unit 45 includes bandpass filters 71 and 72 as described with reference to FIGS. 22A, 22B, 23, and 24, and a drive unit that switches these and arranges them in the optical path. 78 may be included. The light detection unit 45 may output detection values for calculating each parameter relating to each wavefront of the laser beam and the guide laser beam. The controller 48 may calculate parameters relating to the wavefronts of the laser beam and the guide laser beam based on the detection value output from the light detection unit 45. The method for calculating the parameter relating to the wavefront may be the same as the method described in the first and second embodiments. The controller 48 may control the third wavefront adjuster 83 so that the difference between the parameters relating to the wavefronts of the laser beam and the guide laser beam becomes small.
About another point, it may be the same as that of 2nd Embodiment.

  According to the fourth embodiment, it is possible to reduce the difference between the parameters regarding the wavefronts of the laser beam and the guide laser beam in the light detection unit 45. Therefore, if the first or second wavefront adjuster 81 or 82 is controlled based on the parameter relating to the wavefront of the guide laser beam in the light detection unit 55, the wavefront of the laser beam in the light detection unit 55 can be accurately detected from the initial stage of control. It can be controlled. Thereby, the condensing diameter and condensing position of the laser beam irradiated to the target material in the chamber can be stabilized in a short time after the start of laser beam output from the laser device 3.

  The operation of the controller 48 in the fourth embodiment may be the same as the operation of the controller 48 in the third embodiment except for controlling the third wavefront adjuster 83 instead of controlling the guide laser beam wavefront adjuster 84. .

7). EUV light generation system for adjusting the wavefront of a laser beam and the wavefront of a guide laser beam (fifth embodiment)
FIG. 29 is a partial cross-sectional view of an EUV light generation system according to the fifth embodiment. The EUV light generation system according to the fifth embodiment may include a guide laser beam wavefront adjuster 84 in the optical path of the guide laser beam between the guide laser device 40 and the laser beam combiner 44 on the sub-fab floor. . Furthermore, in the fifth embodiment, the first wavefront adjuster 81 may be disposed in the optical path of the output laser beam of the laser device 3. The configurations of the first wavefront adjuster 81 and the guide laser beam wavefront adjuster 84 may be the same as the configurations of the first and second wavefront adjusters 81 in the first embodiment.

  In the fifth embodiment, the light detection unit 45 includes bandpass filters 71 and 72 as described with reference to FIGS. 22A, 22B, 23, and 24, and a drive unit that switches these and arranges them in the optical path. 78 may be included. The light detection unit 45 may output detection values for calculating parameters relating to the wavefronts of the laser beam and the guide laser beam to the controller 48.

  The controller 48 may transmit the detection value output from the light detection unit 45 to the controller 58. The controller 48 or 58 may calculate each parameter regarding each wavefront of the laser beam and the guide laser beam based on the detection value output from the light detection unit 45. When the controller 48 calculates each parameter regarding each wavefront of the laser beam and the guide laser beam, the controller 48 may transmit these parameters to the controller 58.

  The method for calculating the parameter relating to the wavefront may be the same as the method described in the first and second embodiments.

The controller 58 may control the guide laser beam wavefront adjuster 84 so that the difference between the parameters regarding the wavefronts of the laser beam and the guide laser beam becomes small. The control of the guide laser beam wavefront adjuster 84 may be the same as that described with reference to FIG.
About another point, it may be the same as that of 2nd Embodiment.

  According to the fifth embodiment, it is possible to reduce the difference in parameters related to the wavefronts of the laser beam and the guide laser beam in the light detection unit 45. Therefore, if the first or second wavefront adjuster 81 or 82 is controlled based on the parameter relating to the wavefront of the guide laser beam in the light detection unit 55, the wavefront of the laser beam in the light detection unit 55 can be accurately detected from the initial stage of control. It can be controlled. Thereby, the condensing diameter and condensing position of the laser beam irradiated to the target material in the chamber can be stabilized in a short time after the start of laser beam output from the laser device 3.

8). EUV light generation system using a pre-pulse laser (sixth embodiment)
FIG. 30 is a partial cross-sectional view of an EUV light generation system according to the sixth embodiment. In the sixth embodiment, a method may be used in which a target is irradiated with a prepulse laser beam to diffuse the target, and the diffused target is irradiated with a main pulse laser beam to convert the target into plasma. For example, a laser beam with a wavelength of 1.06 μm output from a YAG laser device is used as a prepulse laser beam, and a laser beam with a wavelength of 10.6 μm output from a carbon dioxide (CO ₂ ) laser device is used as a main pulse laser beam. Also good.

  Although depending on conditions such as the diameter of the droplet target and the light intensity of the prepulse laser beam, preplasma can be generated from the surface of the target irradiated with the prepulse laser beam when the target is irradiated with the prepulse laser beam. Pre-plasma refers to a target in which a portion near the surface irradiated with a pre-pulse laser beam is vapor containing ions or neutral particles. Such a phenomenon that pre-plasma is generated is also called laser ablation.

  Alternatively, when the target is irradiated with a prepulse laser beam, the target can be destroyed. The destroyed target can be diffused by a reaction force caused by the ejection of the pre-plasma.

  In this specification, the target including at least one of the pre-plasma generated by irradiation of the pre-pulse laser beam to the target and the destroyed target is referred to as a diffusion target in this specification.

  By irradiating the diffusion target generated by the irradiation with the pre-pulse laser beam with the main pulse laser beam, the diffusion target can be turned into plasma. According to this method, higher energy EUV light is expected to be emitted than a method of generating EUV light by converting the target into plasma using only the main pulse laser beam.

  As shown in FIG. 30, either one of the laser devices 3a and 3b is a prepulse laser device for outputting a prepulse laser beam, and the other is a main pulse laser device for outputting a main pulse laser beam. Good. These laser devices may be arranged on the subfab floor. In this embodiment, the case where the laser device 3a is a pre-pulse laser device and the laser device 3b is a main pulse laser device will be described as an example. When the laser device 3a is a main pulse laser device and the laser device 3b is a prepulse laser device, the prepulse laser device and the main pulse laser device can be interchanged in the following description.

  In a region spanning the sub-fab floor and the clean room floor, the laser beam traveling direction control device 34 may include a beam transmitter 50a. The configuration and operation of the beam transmitter 50a may be the same as the configuration and operation of the beam transmitter 50 in the first embodiment. In the clean room floor, the laser beam traveling direction control device 34 may include a high reflection mirror 59a. These components may be provided to control the traveling direction of the prepulse laser beam output from the prepulse laser apparatus 3a. These components and operations are output from the laser apparatus 3 in the first embodiment. This may be the same as the configuration and operation of the components provided to control the traveling direction of the laser beam.

  In a region spanning the sub-fab floor and the clean room floor, the laser beam traveling direction control device 34 may include a beam transmitter 50b. The configuration and operation of the beam transmitter 50b may be the same as the configuration and operation of the beam transmitter 50 in the first embodiment. In the clean room floor, the laser beam traveling direction control device 34 may include a high reflection mirror 59b. These components may be provided to control the traveling direction of the main pulse laser beam output from the main pulse laser device 3b, and the configuration and operation thereof are the same as those of the laser device 3 in the first embodiment. The configuration and operation of components provided for controlling the traveling direction of the output laser beam may be the same.

  The high reflection mirror 59a may reflect the prepulse laser beam with high reflectivity. The high reflection mirror 59b may reflect the main pulse laser beam with high reflectivity. The prepulse laser beam reflected by the high reflection mirror 59a may be incident on the first surface (the right surface in the drawing) of the beam splitter 56. The main pulse laser beam reflected by the high reflection mirror 59b may be incident on the second surface (the left surface in the drawing) of the beam splitter 56.

  The beam splitter 56 may reflect the prepulse laser beam incident on the first surface toward the high reflection mirror 61 with high reflectivity. Further, the beam splitter 56 may transmit a part of the prepulse laser beam incident on the first surface toward the first beam monitor 57.

  The beam splitter 56 may transmit the main pulse laser beam incident on the second surface toward the high reflection mirror 61 with high transmittance. Further, the beam splitter 56 may reflect a part of the main pulse laser beam incident on the second surface toward the first beam monitor 57.

  The first beam monitor 57 may have a light receiving surface sensitive to the pre-pulse laser beam transmitted through the beam splitter 56 and the main pulse laser beam reflected by the beam splitter 56.

  The beam splitter 56 may function as a laser beam combiner that matches the traveling direction of the prepulse laser beam and the traveling direction of the main pulse laser beam. As a substrate material of such a beam splitter 56, diamond may be used.

  The high reflection mirror 61 may reflect the pre-pulse laser beam reflected by the beam splitter 56 and the main pulse laser beam transmitted through the beam splitter 56 with high reflectivity.

Each laser device may be controlled so that the main pulse laser beam is emitted after a predetermined time has elapsed from the prepulse laser beam emission. The pre-pulse laser beam and the main pulse laser beam sequentially reflected by the high reflection mirror 61 may pass through the window 66 with high transmittance. The pre-pulse laser beam and the main pulse laser beam that have passed through the window 66 may be reflected by the flat mirror 62 with high reflectivity. Thereafter, the pre-pulse laser beam and the main pulse laser beam reflected by the plane mirror 62 may be focused on the plasma generation region 25 by the laser beam focusing mirror 220, respectively. By irradiating the target with a pre-pulse laser beam, a diffusion target is generated. After that, by irradiating the diffusion target with the main pulse laser beam, the diffusion target is turned into plasma, and EUV light can be emitted from the plasma.
About another point, it may be the same as that of 1st Embodiment.

  According to the sixth embodiment, even when the main pulse laser beam is irradiated to the diffusion target after the target is irradiated with the pre-pulse laser beam, the condensing diameters and condensing positions of the pre-pulse laser beam and the main pulse laser beam are set. Can be stabilized.

  Further, the first and second guide laser beams whose traveling directions are made to coincide with the pre-pulse laser beam and the main pulse laser beam are output, and the wavefront adjuster is controlled by detecting the wavefront of the guide laser beam. Good. Control of each wavefront tuner using a guide laser beam may be the same as in the second to fifth embodiments.

9. Configuration of Controller FIG. 31 is a block diagram showing a schematic configuration of each controller such as the EUV light generation controller 5, the controller 48, the controller 58, and the like.
Each controller in the above-described embodiment may be configured by a general-purpose control device such as a computer or a programmable controller. For example, it may be configured as follows.

(Constitution)
The controller includes a processing unit 1000, a storage memory 1005, a user interface 1010, a parallel I / O controller 1020, a serial I / O controller 1030, an A / D, and D / A converter connected to the processing unit 1000. 1040. Further, the processing unit 1000 may include a CPU 1001, a memory 1002 connected to the CPU 1001, a timer 1003, and a GPU 1004.

(Operation)
The processing unit 1000 may read a program stored in the storage memory 1005. The processing unit 1000 may execute the read program, read data from the storage memory 1005 in accordance with execution of the program, or store data in the storage memory 1005.

  The parallel I / O controller 1020 may be connected to devices 1021 to 102x that can communicate with each other via a parallel I / O port. The parallel I / O controller 1020 may control communication using a digital signal via a parallel I / O port that is performed in the process in which the processing unit 1000 executes a program.

  The serial I / O controller 1030 may be connected to devices 1031 to 103x that can communicate with each other via a serial I / O port. The serial I / O controller 1030 may control communication using a digital signal via a serial I / O port that is performed in a process in which the processing unit 1000 executes a program.

  The A / D and D / A converter 1040 may be connected to devices 1041 to 104x that can communicate with each other via an analog port. The A / D and D / A converter 1040 may control communication using an analog signal via an analog port that is performed in the process in which the processing unit 1000 executes a program.

  The user interface 1010 may be configured such that an operator displays a program execution process by the processing unit 1000, or causes the processing unit 1000 to stop program execution or interrupt processing by the operator.

  The CPU 1001 of the processing unit 1000 may perform program calculation processing. The memory 1002 may temporarily store a program during the course of execution of the program by the CPU 1001 or temporarily store data during a calculation process. The timer 1003 may measure time and elapsed time, and output the time and elapsed time to the CPU 1001 according to execution of the program. When image data is input to the processing unit 1000, the GPU 1004 may process the image data according to the execution of the program and output the result to the CPU 1001.

The devices 1021 to 102x connected to the parallel I / O controller 1020 and capable of communicating via the parallel I / O port are the second beam monitor 47 or 57, the EUV light generation controller 5, other controllers, and the like. May be.
The devices 1031 to 103x connected to the serial I / O controller 1030 and capable of communicating via the serial I / O port include a guide laser device 40, a laser beam traveling direction adjusting mechanism 41, a second beam monitor 47 or 57, The beam transmitter 50, the first wavefront adjuster 81, the second wavefront adjuster 82, the third wavefront adjuster 83, the guide laser beam wavefront adjuster 84, and the like may be used.
The devices 1041 to 104x connected to the A / D and D / A converter 1040 and capable of communicating via analog ports may be various sensors such as a temperature sensor, a pressure sensor, and a vacuum gauge.
By being configured as described above, the controller may be able to realize the operations shown in the flowchart.

  The above description is intended to be illustrative only and not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the embodiments of the present disclosure without departing from the scope of the appended claims.

  Terms used throughout this specification and the appended claims should be construed as "non-limiting" terms. For example, the terms “include” or “included” should be interpreted as “not limited to those described as included”. The term “comprising” should be interpreted as “not limited to what is described as having”. Also, the modifier “one” in the specification and the appended claims should be interpreted to mean “at least one” or “one or more”.

  DESCRIPTION OF SYMBOLS 1 ... EUV light generation apparatus, 2 ... Chamber, 3 ... Laser apparatus, 3a ... Pre-pulse laser apparatus, 3b ... Main pulse laser apparatus, 4 ... Target sensor, 5 ... EUV light generation control apparatus, 6 ... Exposure apparatus, 9 ... Installation Mechanism: 10 ... Chamber reference member, 11 ... EUV light generation system, 21 ... Window, 22 ... Laser beam collector mirror, 23 ... EUV collector mirror, 24 ... Through-hole, 25 ... Plasma generation region, 26 ... Target supply device , 27 ... target, 28 ... target recovery part, 29 ... connection part, 31 ... laser beam, 32 ... laser beam, 33 ... laser beam, 34 ... laser beam traveling direction control device, 40 ... guide laser device, 41 ... laser beam Traveling direction adjusting mechanism, 42 ... high reflection mirror, 43 ... high reflection mirror, 44 ... laser beam combiner, 45 ... light detection unit, 46 ... B Sampler 47 ... second beam monitor 48 ... controller 50 ... beam transmitter 50a ... beam transmitter 50b beam transmitter 51 ... high reflection mirror 52 ... high reflection mirror 53 ... high reflection mirror 55 ... Photodetector, 56 ... Beam splitter, 57 ... First beam monitor, 58 ... Controller, 59 ... High reflection mirror, 59a ... High reflection mirror, 59b ... High reflection mirror, 60 ... Mirror storage container, 61 ... High Reflection mirror, 62 ... plane mirror, 66 ... window, 71 ... band pass filter, 72 ... band pass filter, 73 ... beam splitter, 74 ... condensing optical system, 75 ... transfer optical system, 77 ... high reflection mirror, 78 ... Drive unit 79... Transfer optical system 81. First wavefront adjuster 82. Second wavefront adjuster 83. Third wavefront adjuster 84 84 Guide laser beam Wave front modulator, 86 ... plane mirror, 87 ... deformable mirror, 88 ... plane mirror, 90 ... Shack-Hartmann wavefront sensor, 91 ... microlens array, 92 ... screen, 93 ... camera, 220 ... laser beam focusing mirror, 251: Synchrotron radiation, 252 ... EUV light, 291 ... Wall, 292 ... Intermediate focusing point, 300 ... Master oscillator, 301 ... Amplifier, 302 ... Amplifier, 303 ... Amplifier, 304 ... Amplifier, 310 ... Housing, 320 ... Air Suspension, 421 ... Mirror holder, 422 ... Actuator section, 431 ... Mirror holder, 432 ... Actuator section, 500 ... Optical path tube, 511 ... Mirror holder, 521 ... Mirror holder, 522 ... Actuator section, 531 ... Mirror holder, 532 ... Actuator Part, 540 ... beam profiler, 570 DESCRIPTION OF SYMBOLS: Beam profiler, 590 ... Beam profiler, 801 ... Convex mirror, 802 ... Concave mirror, 811 ... Plane mirror, 812 ... Plane mirror, 813 ... Off-axis parabolic concave mirror, 814 ... Off-axis parabolic concave mirror, 815 ... mirror fixing plate, 821 ... off-axis paraboloid convex mirror, 822 ... off-axis paraboloid concave mirror, 823 ... plane mirror, 824 ... plane mirror, 825 ... mirror fixing plate, 851 ... pressure vessel, 852 ... reflector , 853 ... Supply piping, 854 ... Discharge piping, 855 ... Pressure regulator, 871 ... Substrate, 872 ... Insulating layer, 873 ... Lower electrode, 874 ... Piezoelectric member, 875 ... Upper electrode, 876 ... Reflective layer, 1000 ... Processing Part 1001 CPU 1002 Memory 1003 Timer 1004 GPU 1005 Storage memory 1010 User The interface, 1020 ... parallel I / O controller, 1030 ... serial I / O controller, 1040 ... A / D, D / A converter

Claims (9)

A first wavefront adjuster configured to adjust a wavefront of a laser beam output from the laser device;
A beam transmitter configured to transmit a laser beam output from the first wavefront tuner;
A second wavefront adjuster configured to adjust the wavefront of the laser beam output from the beam transmitter;
A beam monitor configured to receive a portion of the laser beam output from the second wavefront tuner, and configured to output a detection value of the received light;
A controller configured to input the detection value and control the first and second wavefront tuners;
A laser beam control device comprising: A guide laser device for outputting a guide laser beam;
A laser beam combiner disposed between the laser device and the first wavefront tuner and configured to substantially match the traveling directions of the guide laser beam and the laser beam;
The laser beam control device according to claim 1, further comprising: A third wavefront adjuster installed between the guide laser device and the laser beam combiner and configured to adjust a wavefront of the guide laser beam;
The controller is configured to input the detection value and further control a third wavefront tuner.
The laser beam control apparatus according to claim 2. A third wavefront adjuster installed between the guide laser device and the laser beam combiner and configured to adjust a wavefront of the guide laser beam;
The laser beam combiner is disposed between the laser beam combiner and the first wavefront adjuster, and is configured to receive a part of the laser beam output from the first wavefront adjuster. A second beam monitor configured to output a second detection value;
The controller is configured to control the third wavefront adjuster by inputting the second detection value;
The laser beam control apparatus according to claim 2. A guide laser device configured to output a guide laser beam;
A laser beam combiner disposed between the first wavefront tuner and the beam transmitter and configured to substantially match the traveling directions of the guide laser beam and the laser beam;
A wavefront adjuster disposed between the guide laser device and the laser beam combiner and configured to adjust a wavefront of the guide laser beam;
The laser beam control device according to claim 1, further comprising:   The laser beam control device according to claim 1, further comprising at least one amplifier disposed between the laser device and the beam transmitter and configured to amplify the laser beam.   The laser beam control apparatus according to claim 1, wherein the detected value is a beam width.   The laser beam control apparatus according to claim 1, wherein the detected value is a parameter relating to a wavefront. A first wavefront adjuster configured to adjust a wavefront of a laser beam output from the laser device;
A beam transmitter configured to transmit a laser beam output from the first wavefront tuner;
A second wavefront adjuster configured to adjust the wavefront of the laser beam output from the beam transmitter;
A beam monitor configured to receive a portion of the laser beam output from the second wavefront tuner, and configured to output a detection value of the received light;
A laser beam controller comprising: a controller configured to input the detection value and control the first and second wavefront tuners;
A chamber provided with an entrance at a position for introducing a laser beam output from the laser beam control device;
A target supply unit provided in the chamber for supplying a target material to a predetermined region in the chamber;
A laser condensing optical system for condensing the laser beam in the predetermined region;
An extreme ultraviolet light generator.

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